Olefins, either alpha-olefins or internal olefins, and either linear or branched, have been used in drilling fluids used in the drilling of subterranean oil and gas wells as well as other drilling fluid applications and drilling procedures.
Workers in the olefins field are searching for better, more efficient, less costly ways to isomerize alpha-olefins to linear internal olefins without increasing branched olefin content.
Several methods are known which achieve isomerization of olefins but are not successful in minimizing branched olefin content and/or have other disadvantages. For example, it is known that such synthetic hydrocarbons can be prepared by oligomerizing one or more olefinic monomers, such as those monomers having a chain length of from C.sub.2 to C.sub.14.
A known method for Isomerizing olefins utilizes platinum supported on a SAPO-11 molecular sieve catalyst. In Gee et al. (U.S. Pat. No. 5,589,442), incorporated herein by reference, the platinum/SAPO-11 catalyst is used to partially isomerize a feed containing C.sub.14 to C.sub.18 olefins, preferably linear olefins, and more preferably normal alpha-olefins. The product is a mixture of linear and branched olefins, with predominately internal olefins. This catalyst is not effective to achieve a mixture which is essentially completely linear internal olefins. Rather, a significant portion of the product is branched and/or alpha-olefins.
Other methods are known which have similar disadvantages. For example, Becker et al. (German Patent No. 4139552) teach isomerization of N-alkenes to iso-alkenes using microporous aluminophosphate catalyst with inert gas hydrogen and alkene-containing hydrocarbon mixture.
Khare et al. (U.S. Pat. No. 5,304,696) teach double bond isomerization of olefinic compounds by contacting an olefinic compound and a sulfated zirconia catalyst.
Heckelsberg (U.S. Pat. No. 3,823,572) teaches converting an olefin hydrocarbon, such as propylene and/or butene, to at least one other olefin hydrocarbon, such as isoamylenes, in a catalytic conversion process utilizing simultaneous or sequential contacting of an olefin reaction catalyst and a skeletal isomerization catalyst.
Suzukamo et al. (Japanese Patent No. 01019027) teach isomerizing olefins into stable internal olefins in the presence of a solid base catalyst prepared by heating at 200-450 degrees in an inert gas an alkali metal hydride and Al.sub.2 O.sub.3 pretreated with an alkali metal carbonate or aluminate.
Slaugh (German Patent No. 2336138) teaches double bond isomerization of normal alkenes at 20-100 degrees over a catalyst composed of a K salt on an activated alumina carrier (pretreated 2-16 hours at 350-700 degrees in a nonoxidizing atmosphere).
The present Applicants have found that nickel supported on a silica/alumina catalyst can be used for the almost complete isomerization of alpha-olefins to linear internal olefins with minimal formation of branched olefins. Such a finding is a major development in the olefins field, because the nickel supported on a silica/alumina catalyst is an economical alternative to previously used catalysts and is actually more effective than prior art catalysts used with this reaction.